When connecting multiple speakers to an amplifier, it's important to stay above the amp's minimum load requirements. Going below an impedance rating can overheat or even damage the amplifier. Fortunately, stereo volume controls with selectable impedance matching provide this means for protection.

An Easy Way to Determine Impedance Match Volume Control Settings

An Easy Way to Determine Impedance Match Volume
Control Settings
by Bob Farinelli,
President and Chief Technical Officer, ELAN
Home Systems

When connecting multiple
speakers to an amplifier, it's important to stay above the amp's minimum
load requirements. Going below an impedance rating can overheat or even
damage the amplifier. Fortunately, stereo volume controls with
selectable impedance matching provide this means for protection.

When connecting multiple speakers to an amplifier, it's important to stay
above the amp's minimum load requirements. Going below an impedance rating can
overheat or even damage the amplifier. Fortunately, stereo volume controls with
selectable impedance matching provide this means for protection.

Models like ELAN Home Systems' VS and VSO stereo volume controls feature 1x,
2x, 4x and 8x configurable jumpers to select the optimum impedance match
setting. What jumper settings to use depends on three numbers:

the minimum impedance rating of the amplifier

the total speakers being connected to the amplifier channel

the impedence of the speakers being connected to the amplifier channel.

After you know these three numbers, it's a simple matter of elementary school
math. It takes two simple equations to determine impedance match settings:

For example, if an amplifier's minimum load impedance rating is 8 ohms, and
you will connect four 8 ohm speakers to an amplifier channel, you'd make two
calculations:

8 ohm speakers / 4 speakers = 2 ohm load impedance (8/4=2)

8 ohm amplifier / 2 ohm load impedance = 4x jumper setting
(8/2=4)

Remember: Most speakers are rated at 4, 6 or 8 ohms. If your speakers aren't
those ratings, you'll need to determine the average impedance. One pair of 4 ohm
speakers is the equivalent of two pairs of 8 ohm speakers. Round up any
fractional jumper setting to the next highest setting available on the volume
control.

Also, all volume controls connected to the amplifier should have the same
impedance match setting.